The present invention relates to a washing machine comprising a washing tub including an upper peripheral wall section which is stationary in a washing mode and a lower peripheral wall section which is rotated clockwise and counterclockwise in the washing mode. More particularly, this invention relates to a washing machine in which laundry is put together with water in the washing tub, and, in the case of a small amount of laundry, the laundry is circulated and washed mainly by a water flow produced by the rotation of the lower peripheral wall section, and, in the case of a large amount of laundry, the laundry is washed by friction with the upper peripheral wall section and its own circulation caused by a frictional force attributed to its contact with the lower peripheral wall section.
In a prior art washing machine of a pulsator type in which the water flow is produced by a pulsator which has vanes or blades projecting therefrom and, the laundry is washed as it follows the cycling water. In the washing machine of this type, therefore, the washing tub requires a capacity large enough to accommodate a specified load size. Thus, only a limited amount of laundry can be washed at a time. If the laundry to be cleaned is too small, the flow of water becomes so intense that the laundry will be excessively washed. If there is too much laundry, on the other hand, the water flow slows down correspondingly, thus lowering the washing efficiency. In the washing machine of this type, moreover, the laundry touches the pulsator only accidentally and partially. It is therefore impossible to produce a satisfactory rub- or friction-washing effect for the entire load. Thus, the washing action of the washing machine of this type is uneven and is liable to damage the laundry.
Meanwhile, a washing machine without a pulsator has recently been proposed in which a washing tub containing water and laundry therein is intermittently rotated as a whole, deriving a washing effect from the difference in circulating speed between the water and laundry. Although the washing machine of this type is not liable to damage the laundry, the washing efficiency is low because of the simple motion of the laundry therein, which is attributed to the small difference between the circulating speeds of the water and laundry.